I have a P31 Neo V2 (MS-7392) with a QuadCore Intel Core 2 Quad Q9550, 2833 MHz (8.5 x 333) and 2GB of Ram.On windows xp the system runs and installs fine.

Now, I want to install a legal copy of Windows 7, but the install locks up.Starting install works, can create the partition, can select OS language etc. Then install starts to copy windows files, still all is fine.After this bit, the extracting of files starts, and eventually stalls. The whole machine freezes!

After reading through a load of internet pages, I have figured out that all peripherals need to be disconnected (USB, additional PCI cards, etc), which I did... restart of installation same issue.

Doing some more read work... loads of people have issues with the AHCI of the SATA drives. Turn it off, they say.unfortunately... I cannot find the option to disable the AHCI in the bios... it's just not there!I hope someone else can help me out on finding the option... but... probably I cannot use this MB with Windows 7, unless MSI comes up with the option to disable AHCI.

Yes, I know AHCI greatly improves performance on the SATA drives, but for now... I'd like to install Windows 7 and start testing it on my system, for future use in the company. You know, testing of all applications written still work, etc, etc.

Doing some more read work... loads of people have issues with the AHCI of the SATA drives. Turn it off, they say.unfortunately... I cannot find the option to disable the AHCI in the bios... it's just not there!I hope someone else can help me out on finding the option... but... probably I cannot use this MB with Windows 7, unless MSI comes up with the option to disable AHCI.

Your are definately on the wrong track here. The P31 Neo V2 has an ICH7 Chipset which does not even support AHCI. But even if it did support AHCI, this would definately not be the cause of your problem because usually, when people have a problem with the Controller in AHCI Mode, the problem is related to Windows XP only (it does not include any AHCI Drivers) or that fact that the generic Vista or W7 AHCI Drivers are not good enough to ensure flawless operation. All of these issues can be solved by integrating the proper Intel AHCI Drivers for the SATA Controller. But again: Your board does not support AHCI but the Intel ICH7 SATA Controller runs in IDE/Compatibility mode. There are no drivers available (or needed) for this operating mode.

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unless MSI comes up with the option to disable AHCI.

All MSI Desktop Mainboards I know of (that support AHCI Mode) have an option to enable or disable this mode in BIOS. Your board does not have such an option because the chipset does not support it in the first place. The cases you read about probably have to do with certain notebooks that are sold with a preinstalled Vista version. The problems usually occur when people decide to install Windows XP without being aware that XP does not include any AHCI Drivers.

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The whole machine freezes!

There are a number of possible explanations for that. A memory problem is often something that causes the system to freeze.

Please make a signature, like I have with all your computers components, including all psu specs (amps, on +12V, 3V, 5V etc ), this way we can help you better.As to your problem, is your XP running normal i.e. no bluescreen freezes etc?Then try HDtune and check your disk status, might be a HD problem, because it freezes on expanding files and thats when HD activity is greatest.http://www.hdtune.com/